我正在尝试pip install --upgrade pip在Docker容器内，但出现错误：

Exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 209, in main
    status = self.run(options, args)
  File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 328, in run
    wb.build(autobuilding=True)
  File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 748, in build
    self.requirement_set.prepare_files(self.finder)
  File "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 360, in prepare_files
    ignore_dependencies=self.ignore_dependencies))
  File "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 577, in _prepare_file
    session=self.session, hashes=hashes)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 810, in unpack_url
    hashes=hashes
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 649, in unpack_http_url
    hashes)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 842, in _download_http_url
    stream=True,
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 480, in get
    return self.request('GET', url, **kwargs)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 378, in request
    return super(PipSession, self).request(method, url, *args, **kwargs)
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 468, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 597, in send
    history = [resp for resp in gen] if allow_redirects else []
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 113, in resolve_redirects
    raise TooManyRedirects('Exceeded %s redirects.' % self.max_redirects)
TooManyRedirects: Exceeded 30 redirects.

有谁知道这是什么原因，和/或如何解决？